Polyisocyanates and a method for their preparation are disclosed in U.S. Pat. No. 2,855,421. This patent discloses a process in which a polyalcohol such as a dihydric or a mixture of a trihydric alcohol and dihydric alcohol is added to a diisocyanate at a somewhat elevated temperature. The diisocyanate is dissolved in an inert solvent such as ethyl acetate. It is noted that the use of trihydric alcohol should accompany a dihydric alcohol for the conditions employed in U.S. Pat. No. 2,855,421. This patent teaches a ratio of isocyanate groups to hydroxy groups of less than 2/1. If neat trihydric alcohol was used only, then after about 3/4 trihydric alcohol was reacted with diisocyanate, the solution would become very viscous and would eventually gell. One advance of my invention over this patent is based on the ratio of reactants, wherein, the ratio of isocyanate groups groups per hydroxyl group is between 4/1 and 10/1.